Debunk: Predators Kill Only Lame, Sick and Weak Prey Species

I have finally found a written explanation about predator/prey relationships that is easy to sink your teeth into and understand and written by an authority on the subject; Dr. Charles Kay, Wildlife Ecology-Range Management Specialist Utah State University. His article can be found in Muley Crazy Magazine, Jan./Feb. Edition 2013.

Anyone paying any attention to the emotional debates about large predators – wolves and coyotes seem to carry the most irrational emotions – have heard someone, even those supposedly who are authorities, say that wolves/coyotes/large predators are necessary for our ecosystems because they kill only the lame, sick, weak and/or substandard members of the prey species. With the mindless perpetuation of such drivel, we are also told this “sanitary” engineering by predators provides for “healthy” prey species, some even claiming this natural phenomenon limits and reduces certain wildlife diseases because these predators are killing the sick among the prey.

I have always contended that if large predators were intelligent enough to determine the sickly of the species, why aren’t they equally intelligent to pick a good meal rather than one that might taste bad and be full of worms and disease? But I guess maybe that’s another discussion.

What studies that do exist, clearly show that large predators kill their prey/food depending upon several factors, none of which are the result of a predator recognizing they have a sick animal on their hands. Factors include: How easy it is for predators to kill their prey species under normal conditions; the size and killing ability of the predator versus the size and defense capabilities of the prey; how the predator hunts and environmental conditions. Seriously, is this something new? Of course not.

Dr. Kay explains that any prey species that is easily captured and killed, there is no difference in the proportionate killing of healthy vs. ill prey species. As the size and defense capabilities of the predator animal increases, the incidence of prey killed increases mostly do to a reduction of defensive capability.

Kay uses an example of lynx in Europe that will feed on both roe deer and red deer. He explains that roe deer, “are less than half the size of mule deer, while red deer are the same species as our elk.” Roe deer are easier to catch for the lynx and kill without evidence of taking a disproportionate number of sick roe deer. As far as the red deer are concerned, because the animal is bigger and more difficult to catch and take down, lynx tend to target red deer calves in disproportionate numbers to the overall red deer population. A bigger predator, such as a wolf, isn’t choosy between roe deer and red deer and will take either species that is available when hunted with little or no regard to seeking out a sick member of the herd.

All predators hunt differently; some are ambush hunters, some are stalkers that run down their prey, for examples. An ambush hunter isn’t particular or concerned over whether an animal is sick or lame. Essentially they have one shot at their prey, healthy or not. On the other hand, a predator, like a wolf or coyote, track down their prey, sometimes running them down, or perhaps surrounding their target. In this case, opportunism will likely afford the predator a better chance at catching up to and killing a sick or lame prey species. This only makes sense.

As any good scientist would do, Dr. Kay points out information he provided in other research work written about in “Predation and the Ecology of Fear” [see Muley Crazy 10(5): 23-28; 2010]. In this work and subsequent reporting, Kay points out that often times the substandard prey species can become this way due to harassment by predators and humans. Predators torment and harass prey species constantly. Battle weary prey animals then become an easier target and thus the ill health mythology exploited by the predator protectors is not so because it is caused by natural conditions such as physical defects and disease.

And if predators, such as wolves, exist for the function of killing only the lame, diseased and infirm of prey animals, while yielding us a “healthy” ecosystem, how does one explain surplus killing? Surplus killing, which is readily recorded, is when wolves move into a herd of prey and just kill everything they can until they have had enough killing, for no apparent reason than to kill. Some think of it as a learning adventure for the immature dogs in the pack. What I can tell you is that those who protect predators will deny that surplus killing is real.

Depending upon the region in which predator and prey relationships are being examined, one can find many environmental conditions that will effect a predator’s ability to hunt and a prey’s ability to defend themselves or escape. Deep and crusty snow comes to mind, as often prey species such as deer and moose, that use running as an escape, cannot flee so easily and wolves and coyotes easily run them down.

Dr. Kay also debunks the notions that large predators are good to limit or reduce wildlife disease because they pick on the sick prey and not the healthy. He points out that, “Wolf predation has not lowered the incidence of brucellosis in elk within the Yellowstone ecosystem.” Also, “In Canada’s Wood Buffalo National Park, bison are infected with both brucellosis and bovine tuberculosis. Yet more than 50 years of wolf predation has not lowered the incidence of either disease.” Again, “Cape buffalo are preyed upon by African lions and spotted hyenas, both formidable predators, yet predation has not slowed the spread of bovine tuberculosis in Kruger’s cape buffalo population.” Finally, “predation by black bears, mountain lions, and coyotes has not slowed the spread of chronic wasting disease.”

In addition to revealing that predation is not changing the incidences of disease, Dr. Kay tells his readers that some predators, such as wolves and coyotes, carry more than 30 diseases that they are infecting ungulate populations with, and creating for potential harm and possible death to humans. Certainly a predator spreading so many diseases cannot and is not making for a healthy prey population, but an unhealthy one.

Proper control of predators is the proven and scientific method of keeping healthy prey and predator species, not some myth that these predators are like trained physicians making house calls to keep all their food supply healthy. Let’s not pretend.

It is certainly one thing to want to protect your favorite wild animal but at what expense? Do we risk the health of humans while hiding behind some notion that predators are sanitation engineers? As Dr. Kay says, “the next time some wolf biologist or pro-wolf advocate tries to tell you that predators only kill the lame, the sick, and the infirm, or that predators help control disease, listen politely, or not, and then have a good laugh! What you do next is up to you, but remember, the federal government has warned all its employees, who normally handle wolves or wolf scat, about Echincoccus granulosus, but has yet to pass a similar warning on to the general public.”